Cell to cell comunication can either be direct or indirect. Direct communications occur through cell to cell junctions such as gap junctions, tight junctions, adehrens junctions and desmosomes. There are 3 factors that act to bind cells together. Glycoproteins in the glycocalyx act as an adhesive. Wavy contours of the membranes o adjacent cells fit together in a tongue and groove fashion, Special cell junctions form the most important factor; secuing cells together.
Tight Junctions
Tight junctions are a series of integral protein molecules in the plasma membranes of adjacent cells that fuse together. It involves transmembrane proteins claudin and ocludin and is common near the apical region and is an impermeable junction that separates apicl and basal surfaces. They completely encircle the cell and form an adhesion belth. It is seen in epithelial cells in the digestive tract.
Adherens Junctions
Also known as intermediat unctions or zonula adherens. Adheren junctions are located below the tight junctions and forms an adhesion belt. The linker protein cadherins are linked to the actin inside the cells. Since it is connected to actin it has contractile property.
Desmosomes
Anchoring junctions adjacent cell are held together by thin linker protein filaments (cadherins) with plasma membrane thickening on the inside of cells (plaque). The intermediate filaments (keratin) insert into plaques from cytoplasmic side and the cadherins extend from plaque and connect two membranes. It is abundant in tissues subjected to great mechanical stress such as skin and heart muscle. It reduces the chace of tearing, twisting and stretching.
Gap Junctions
This is a communication junction. Cells are colelcted by connexons which are hollow cylinders (transmembrae proteins). Connexon is a protein complex formed by many connexins with a hydrophilic pore. It allows ions, simple sugars and other small molecules to pass trough these water filled channels from one cell to the next. They are present in electrically excitable tissues such as heart andsmooth muscle.
Hemidesmosomes
These are found at the base of the epithelial cells. They anchor the epithelial cell to basal lamina. Integral molecules (transmembrane link protein) conect kerain in the cell to basal lamina.
Chemical Communication
This communication is mediated byc hemicals. The messenger is produced by the source cell and is released by secretion. It travels to the target cell which has receptors and binds to the receptor which trigers a response. Between cells the messengers are neurotrasmiters and hormones, between organs the messengers are hormones and within cells the messengers are second messenger systems and enzyme cascades but all of these operate via receptor in teh cell membrane.
Chemical communication can be classified as pracrine in which chemical acts on another cell which is located close o the cell from which ti is released. Endocrine in which the chemical acts on another cell which is lcoate far away from the cell from which it is released and utilises the bloodstream as a transport system. Autocrine in which the chemical acts on the same cell from which it is released often a mechanism for limiting release of the chemical and neurocrine in which the chemical is released from a neuron and acts on another neuron or other target cell.
Neurotransmitters
If the chemical signal diffuses from the neuron across a narrowextracellular space to a target cel, it is called a neurotransmitter. Thus neurons communicate directly with the cells they innervate by relasing neurotransmitters which are very short range chemical messengers.
Hormones
These are molecules which allow cell to cell communication and are made in gland(s) or cells and are transported by the blood to activate physiological responses. They provide communication which allows one cell to regulate the activity of another cell. They are also distant target tissue receptors and act on cells which are located far away from the cell from which they are released.
Receptor
These are cell membrane or intracellular receptor proteins. They act as sensors with specialised cells or structures that convert various stimuli into electrical signals. Receptors provide site sepcific activity and diversity of responses.
Chemical Messengers
Chemical messengers can be lipophobic or lipophilic. Lipophobic messengrs arewater soluble but not lipid soluble and so dissolve in plasma but do not cross the cell membrane and so act on receptors on teh cellmembrane and include glycine, GABA and catecholamines. Lipophilic messengers are lipid soluble but not water soluble and so bind to carrier proteins in the bood and easily cross the cell membrane and so act on receptors that are inside the cell and include steroid hormones.
Ionotropic and Metabotropic Receptors
Ionotropic receptors gate an ion channel while metabotropic receptors influence the metabolim of a cell and include G-protein coupled receptors and receptor kinases.
Second Messengers
Metabotropic receptor responses activate amplifier enzymes that create intracellular second messengers. Second messengers alter the gating of ion channels and so increase intracellular calcium and change enzme activity (protein kinases or protein phosphatases). Different second messengers include calcium, cyclic AMP, Cyclic GMP, inositol triphosphate and diaceyl glycerol.
Learn More
Learn.Genetics: The Inside Story of Cell Communication
Cell Communication
Bozeman Science: Cell Communication
Cell Connection and Communication
Cell Junctions
Purpose Games: Can you Pick the cell junction?
Purpose Games: Cell Junctions
Questions
Tight Junctions
Tight junctions are a series of integral protein molecules in the plasma membranes of adjacent cells that fuse together. It involves transmembrane proteins claudin and ocludin and is common near the apical region and is an impermeable junction that separates apicl and basal surfaces. They completely encircle the cell and form an adhesion belth. It is seen in epithelial cells in the digestive tract.
Adherens Junctions
Also known as intermediat unctions or zonula adherens. Adheren junctions are located below the tight junctions and forms an adhesion belt. The linker protein cadherins are linked to the actin inside the cells. Since it is connected to actin it has contractile property.
Desmosomes
Anchoring junctions adjacent cell are held together by thin linker protein filaments (cadherins) with plasma membrane thickening on the inside of cells (plaque). The intermediate filaments (keratin) insert into plaques from cytoplasmic side and the cadherins extend from plaque and connect two membranes. It is abundant in tissues subjected to great mechanical stress such as skin and heart muscle. It reduces the chace of tearing, twisting and stretching.
Gap Junctions
This is a communication junction. Cells are colelcted by connexons which are hollow cylinders (transmembrae proteins). Connexon is a protein complex formed by many connexins with a hydrophilic pore. It allows ions, simple sugars and other small molecules to pass trough these water filled channels from one cell to the next. They are present in electrically excitable tissues such as heart andsmooth muscle.
Hemidesmosomes
These are found at the base of the epithelial cells. They anchor the epithelial cell to basal lamina. Integral molecules (transmembrane link protein) conect kerain in the cell to basal lamina.
Chemical Communication
This communication is mediated byc hemicals. The messenger is produced by the source cell and is released by secretion. It travels to the target cell which has receptors and binds to the receptor which trigers a response. Between cells the messengers are neurotrasmiters and hormones, between organs the messengers are hormones and within cells the messengers are second messenger systems and enzyme cascades but all of these operate via receptor in teh cell membrane.
Chemical communication can be classified as pracrine in which chemical acts on another cell which is located close o the cell from which ti is released. Endocrine in which the chemical acts on another cell which is lcoate far away from the cell from which it is released and utilises the bloodstream as a transport system. Autocrine in which the chemical acts on the same cell from which it is released often a mechanism for limiting release of the chemical and neurocrine in which the chemical is released from a neuron and acts on another neuron or other target cell.
Neurotransmitters
If the chemical signal diffuses from the neuron across a narrowextracellular space to a target cel, it is called a neurotransmitter. Thus neurons communicate directly with the cells they innervate by relasing neurotransmitters which are very short range chemical messengers.
Hormones
These are molecules which allow cell to cell communication and are made in gland(s) or cells and are transported by the blood to activate physiological responses. They provide communication which allows one cell to regulate the activity of another cell. They are also distant target tissue receptors and act on cells which are located far away from the cell from which they are released.
Receptor
These are cell membrane or intracellular receptor proteins. They act as sensors with specialised cells or structures that convert various stimuli into electrical signals. Receptors provide site sepcific activity and diversity of responses.
Chemical Messengers
Chemical messengers can be lipophobic or lipophilic. Lipophobic messengrs arewater soluble but not lipid soluble and so dissolve in plasma but do not cross the cell membrane and so act on receptors on teh cellmembrane and include glycine, GABA and catecholamines. Lipophilic messengers are lipid soluble but not water soluble and so bind to carrier proteins in the bood and easily cross the cell membrane and so act on receptors that are inside the cell and include steroid hormones.
Ionotropic and Metabotropic Receptors
Ionotropic receptors gate an ion channel while metabotropic receptors influence the metabolim of a cell and include G-protein coupled receptors and receptor kinases.
Second Messengers
Metabotropic receptor responses activate amplifier enzymes that create intracellular second messengers. Second messengers alter the gating of ion channels and so increase intracellular calcium and change enzme activity (protein kinases or protein phosphatases). Different second messengers include calcium, cyclic AMP, Cyclic GMP, inositol triphosphate and diaceyl glycerol.
Learn More
Learn.Genetics: The Inside Story of Cell Communication
Cell Communication
Bozeman Science: Cell Communication
Cell Connection and Communication
Cell Junctions
Purpose Games: Can you Pick the cell junction?
Purpose Games: Cell Junctions
Questions
- Disappearance of which type of junction most likely contributs to the metastasi of cancer cells throughout the body
- name the different mechnisms through which cells can communciate with each other.